The present invention relates to a disk brake suitably used to apply braking force to a vehicle, for example, an automobile.
In general, a disk brake provided on a vehicle, e.g. an automobile, includes a mounting member secured to a non-rotating part of a vehicle. The mounting member has a pair of arms spaced apart from each other in the rotational direction of a disk. The pair of arms extend over the outer periphery of the disk in the axial direction of the disk. A caliper is slidably provided on the arms of the mounting member to press a pair of friction pads against both sides of the disk. A pair of pad springs are attached to the respective arms of the mounting member to resiliently support the pair of friction pads between the arms [for example, see Japanese Utility Model Application Public Disclosure (KOKAI) No. Hei 5-89978].
This type of conventional disk brake operates as follows. When the driver of the vehicle conducts a braking operation, a piston provided on the inner side of the caliper is forced to slide toward the disk by an externally supplied hydraulic pressure, causing the inner friction pad to be pressed against the disk. Counterforce produced at this time causes the caliper to be slidingly displaced relative to the mounting member. Consequently, the friction pads are pressed against both sides of the disk between the outer claw portion of the caliper and the piston, thereby applying braking force to the rotating disk.
The arms of the mounting member are provided with pad guides for slidably guiding the pair of friction pads in the axial direction of the disk. The pad springs suppress rattling of the friction pads against the pad guides of the arms or the like and allow smooth sliding displacement of the friction pads.
The pad springs are formed, for example, by pressing resilient metal plates or the like. Of the pair of pad springs, the one that is located at the entrance side in the rotational direction of the disk (this side will hereinafter be referred to as “entrance side”) is provided with pad-urging spring members extending obliquely to the axial direction of the disk. The pad-urging spring members are each formed by folding the proximal end portion of an elongated plate-shaped spring member in a substantially U shape. The pad-urging spring members urge the respective friction pads in the rotational (circumferential) direction of the disk.
The pad spring that is located at the exit side in the rotational direction of the disk (this side will hereinafter be referred to as “exit side”) is provided with pad-retaining plate portions that bear braking torque acting on the friction pads in cooperation with the exit-side arm. The pad-retaining plate portions suppress the friction pads from being displaced relative to the mounting member in the rotational (circumferential) direction of the disk.
In the above-described prior art, the entrance-side pad spring is provided with pad-urging spring members to suppress rattling of the friction pads in the rotational direction of the disk. Each pad-urging spring member is, however, formed by folding the proximal end portion of an elongated plate-shaped spring member in a substantially U shape. The distal end portion of the pad-urging spring member extends obliquely to the axial direction of the disk.
Accordingly, the pad spring of the prior art suffers from the following problem. The pad-urging spring members are each formed as an elongated plate-shaped spring member extending obliquely to the axial direction of the disk. Therefore, urging force (spring load of the pad-urging spring members) that urges the friction pads in the rotational (circumferential) direction of the disk differs considerably when the friction pads are new and when they have become worn. Therefore, it is difficult to keep the urging force constant.
In addition, each pad-urging spring member has a substantially U-shaped folded portion at the proximal end thereof. The folded portion undesirably extends to a considerable extent axially outward of the disk from the pad guide of the mounting member. Therefore, the folded portions of the pad-urging spring members are likely to interfere with the assembling operation when the pad springs are attached to the mounting member and the friction pads are fitted to the pad springs. If external force is applied to the folded portion of any pad-urging spring member by accidental touch during the assembling operation, the overall urging force of the pad-urging spring member may be varied unfavorably.
Moreover, because the pad-urging spring members are elongated plate-shaped spring members extending obliquely to the axial direction of the disk, the urging direction for the friction pads is undesirably tilted at an angle to the plane of the disk, causing the friction pads to tilt with respect to the disk. The unstable attitude of the friction pads causes deterioration of the sliding properties of the friction pads.